A332986 Successive differences of index of triangular numbers sum of two pentagonal numbers.

1, 4, 6, 18, 2, 7, 1, 4, 1, 2, 4, 5, 5, 3, 1, 2, 2, 5, 3, 3, 4, 3, 1, 10, 1, 1, 8, 3, 4, 7, 5, 12, 10, 8, 9, 7, 3, 5, 3, 6, 3, 10, 11, 1, 2, 13, 9, 6, 3, 2, 1, 2, 3, 3, 2, 2, 6, 13, 9, 4, 1, 11, 1, 3, 8, 9, 1, 4, 6, 3, 8, 3, 5, 2, 3, 2, 5, 1, 14, 9

Offset: 1

Author

Olivier Gérard, Mar 05 2020

Keywords

• nonn

Comments

The behavior of this sequence is unexpectedly quite complex.

Links

• Peter Kagey, Table of n, a(n) for n = 1..2500

Crossrefs

Cf. A000217 (triangular numbers), A000326 (pentagonal numbers), A332987 (sums of two nonzero pentagonal numbers), A333009 (analog for indices of square numbers).

Cf. First differences of A332985.